is interesting there: it’s an SVG element. SVG and MathML are fun in HTML syntax, because it becomes a little more XMLly when parsing them: XML-style self-closing tags ( ) actually work , and there’s no such thing as a void element (e.g. which has no closing tag because it has no contents). This can lead to fun problems in overly-simplistic filtering, e.g. alert() is a syntax error in SVG or in XML-syntax HTML, is sw…
Yeah the trailing slash cargo cult just goes to show the author has no idea what he/she is doing. Even more pointless is a pretentious space before the slash. It appears many extant uses of the bogus slash result from WordPress filters and their fragile nature (never change a running WP system aka WP trainwrecks) rather than manual insertion.
It could also be an habit, and not really a harmful one. You can argue against it with convincing arguments, but in the end, there's nothing fundamentally wrong with it. It's understood by the parser.
The space before the slash once was advised for compatibility with old browsers when writing polyglot html. Some old browsers would not understand the slash, but this would not be an issue with a space. This is mostly irrelevant today but habits stick.
And with the gotcha exposed by my sibling comment, maybe it's better to stick with the space after all when using the slash. And I can see how wanting to explicitly close the tag is compelling, even if it has its drawbacks.